Accenta G4 mini LCD alarm problems

[Flummaxed]

Hi, I appear to have the same problem as Noopy66 did recently. The alarm bell was triggered last night (at 3am), but making a different noise to the normal alarm sound from the bell box. The noise sounded very much like a buzzer. (two tone but tones of quite close frequency). Strobe was not flashing. I managed to stop the noise by turning off the mains supply.

I bought a new battery today. On opening up the panel, the +ive battery terminal and spade connector was badly corroded with only a few millivolts showing on test meter when disconnected from panel. (It must have been 4-5 years old). I cleaned inner board components and fitted a new spade connector on +ive lead. Checked all fuses on the board, all were ok).
I connected the new battery, closed the panel. All seemed ok. LCD display lit up normally.
A quick alarm test showed it to work ok, using battery power only.
However, when turning the mains supply back on the weird two tone noise started again, but again this only came from the bell box - no sound from internal speaker.
I'm unable to physically check the bell box as I've no ladder these days. So at present the battery is out, and mains supply off.
Any ideas or suggestions would be greatly appreciated. Thanks in advance.



Read more: https://www.diynot.com/diy/conversations/accenta-mini-g4-lcd-alarm.35710/#ixzz6klysdDFy

 

[sparkymarka]

Post picture of pcb .....check voltage on bell output ( on battery only) ....bell + and scb connections ....check on dc ....should be 13.8 v Now check on ac range ...note voltage
Now re check with the mains on ....both dc and ac range

 

[Flummaxed]

Thanks, I'll give that a go tomorrow......

 

[Flummaxed]

Hi, Photo attached of PCB, it's dated 2008, I installed it in 2009.

I've now checked the voltages across Bell + and SCB, the results were:

Condition

No Mains & No Battery 0.2 mV DC
No Mains & No Battery 0.0 V AC

Battery Only (*) 11.41 V DC
Battery only 0.0 V AC

Battery & Mains (+) 12.82 V DC
Battery & Mains 0.0 V AC
(*) Normal alarm sound when battery attached (panel open > Tamper)
(+) Weird buzzing from alarm box when mains connected. Stops when mains is off.
When battery disconnected normal siren sound but dies rapidly after only about 2-4 seconds.

Since the alarm box is silent when no power or battery is attached, I would guess that the battery in the Alarm box is dead, or that there is a fault in the battery box. Would you agree?
Any thoughts or suggestions would be greatly appreciated.

 

[sparkymarka]

Well that burnt resistor isn’t going to help
Would also probably say the bellbox battery Is faulty also

 

[Flummaxed]

Thank you very much Sparkymarka. Well spotted. (My eyes aren't the same these days)